Method of vibroabrasion treatment of small-sized parts

ABSTRACT

According to the method proposed herein, in an inert liquid medium are introduced abrasive powder and metallic bodies or particles which are capable of fixing the particles of abrasive powder on their surface and grinding these while interacting with said abrasive powder in the course of treatment of the smallsized parts involved, said abrasive powder that is introduced into said inert liquid medium, should feature its granularity permissible to perform the initial stage of treatment of the small-sized parts involved e.g. coarse grinding, whereas the quantitative ratio between the metallic bodies and abrasive powder that are introduced into said liquid medium, must be so selected as to provide a successive and complete grinding of abrasive powder till obtaining its granularity necessary to perform the final stage of treatment of said small-sized parts e.g. buffing.

United States Patent 389,552 9/1888 Dean Appl. N0. 806,725 Filed Mar.12, 1969 Patented Aug. 10, I971 METHOD OF VIBROABRASION TREATMENT OFSMALL-SIZED PARTS 5 Claims, No Drawings U.S.Cl.... 51/316 Int. Cl B24b1/00 FieldoiSearch .51/313, 314, 315, 316, 317,7,164.5

References Cited UNITED STATES PATENTS Primary Examiner-Lester M.Swingle Attorney-Waters, Roditi, Schwartz & Nissen ABSTRACT: Accordingto the method proposed herein, in an inert liquid medium are introducedabrasive powder and metallic bodies or particles which are capable offixing the particles of abrasive powder on their surface and grindingthese while interacting with said abrasive powder in the course oftreatment of the small-sized parts involved, said abrasive powder thatis introduced into said inert liquid medium, should feature itsgranularity permissible to perform the initial stage of treatment of thesmall-sized parts involved e.g. coarse grinding, whereas thequantitative ratio between the metallic bodies and abrasive powder thatare introduced into said liquid medium, must be so selected as toprovide a successive and complete grinding of abrasive powder tillobtaining its granularity necessary to perform the final stage oftreatment of said small-sized parts e.g. buffing.

METHOD OF VIBROABRASION TREATMENT OF SMALL-SIZED PARTS The presentinvention relates to methods of vibroabrasion treatment of small-sizedparts, mainly for precision instruments that have friction surfaceswhose finish should conform to the highest quality grades.

Widely known in the art is a method of vibroabrasion treat- 'ment ofsmall-sized parts with abrasive powder in an inert liquid medium.

The above-said method, however, suffers from numerous substantialdisadvantages such as: low productivity; repetitive operations of themethod due to the fact that a coarse-grained abrasive powder must beemployed at the initial stage of the grinding process and a fine-grainedpowder must be employed at the'final stage thereof; the necessity foruseof high-dispersive homogenously grained abrasive powders at the finalstage of treatment; impossibility to obtain surfaces finished to aquality that should meet high requirements specified for a varietyofcomponents made use of in precision instruments such as pivots ofelectric measuring instruments; and the fact that in treating parts thestock is removed mostly from protruding parts thereof.

Another method of vibrotreatment is in an inert liquid medium with theuse of abradant-bearing filling agents.

This method though more productive, suffers from all the disadvantagesinherent in the method of vibrotreatment with v abrasive powder and,moreover, involves the use of specially prepared filling agent.

lt is an object of the present invention to eliminate the disadvantagesmentioned above.

It is the main object of the present invention to provide a method ofvibrotreatment of small-sized parts, whereby said parts passuninterruptedly through all the process stages at one cycle, startingfrom the coarse and up to the finest one (coarse grinding, finegrinding, buffing), with the possibility to vary the amountof the stockremoved and the rate of its removal from the protruding parts.

Said object is accomplished due to the fact that in an inert liquidmedium are introduced abrasive powder and metallic bodies, said bodiesbeing capable, while interacting with abrasive powderin the course oftreatment of small-sized parts, of

fixing abrasive powder particles on their surface and grindingaforementioned metallic bodies capable of fixing the particles ofabrasive powder on their surface to grind them.

Both abrasive powder and the metallic bodies capable of 1 fixing theabrasive powder particles on the surface thereof, are

introduced into an inert liquid medium constituted by at least twofluids different in viscosity.

The method disclosed herein allow the performance of an entire cycle oftreatment (i.e. coarse grinding, fine grinding, polishing, polishing andbuffing) without changing the inert liquid medium, abrasive powder andmetallic bodies capable of fixing the abrasive powder particles on thesurface thereof, since in the course of treatment, successivelydecreasing partieles of abrasive powder are fixed on the metallicbodies.

The method in question makes it possible to vary the rate of removal andthe amount of the stock removed from the protruding portions of theparts being treated, by varying the ratio between the differentlyviscous fluids constituting the inert liquid medium involved.

The herein-proposed method prevents foreign objects from contacting thesurface of the parts being treated thus eliminating possible adverseeffect of said objects upon the quality of surface finish obtained.

The present method does not involve the use of high-dispersive abrasivepowders, inasmuch as the latter are formed as a result of grindinglarger grains of the initially introduced abrasive powder.

According to the herein-considred method, in the course of treatment ofparts their superficial strengthening simultane- EXAMPLE I Treatment ofcarbon-steel blanks of pivots for electric measuring instruments isinvolved, the length of a blank being equal to 3 mm. and its diameterequal to 0.5 mm. The blanks are to be treated until a fillet radius of35 microns is obtained, with simultaneous grinding, polishing andbuffing of the blank tapered portion.

In a container holding l0 cc. of an inert fluid constituted by 9 cc. ofkerosene and 1 cc. of bone oil, are introduced 300 mg. of abrasivepowder 25 grams of 1.3 mm. diameter globules or pellets made of high-tinbronze, and 1000 blanks of pivots.

This done, the above-mentioned container is imparted oscillating motionat a frequency of 50 c./s. and an amplitude of 4 mm. ln 25 hours thetreatment cycle is completed.

' Then the inert fluid is drained off, whereas a mixture of parts andglobules is rinsed in gasoline and dried. Next the finished pivots areseparated out from the globules by sieving through a rectangular-meshscreen. The globules are employed for treating fresh lots of parts.

The fillet radius of the finished pivots equals 35 microns, the qualityof surface finish on both the tapered portion and the fillet of pivotsbeing in compliance with the highest quality grades. No traces oftreatment are found on the finished surface when investigated under amicroscope of a magnification. Moreover, the finished pivots when usedin electric measuring instruments, feature their abrasion-resistanceunder a vibratory load l.5 times as high as compared to those treated byany other methods, this being due to the fact that they have been givenadditional superficial strengthening in the course of treatment.

EXAMPLE 2 Treatment of carbon-steel blanks of pivots for electricmeasuring instruments is involved, the length of a blank equaling 3 'mm.and its diameter 0.5 mm. The blanks are to be treated until a filletradius of 20 microns is obtained, with simultaneous grinding, polishingand buffing of the blank tapered portion.

In a container holding 10 cc. of an inert fluid composed of 8 cc. ofkerosene and 2 cc. of bone oil, are introduced 120 mg. of abrasivepowder, l5 grams of 1 mm. diameter globules or pellets made of high-tinbronze, and i000 blanks of pivots.

Thereupon the container is imparted oscillating motion at a frequency of50 c./s. and an amplitude of 4 mm. The treatment cycle is to take aperiod of 20 hrs., whereupon the inert fluid is drained off and amixture of parts and globules is washed in gasoline and dried.

Then the finished pivots are separated out from the globules by sievingthrough a rectangular-mesh screen, whereafter the globules are ready tobe used for treating fresh lots of parts. The fillet radius of thefinished pivots equals 20 microns, the quality of surface finish on boththe tapered portion and the fillet of pivots is found to meet thehighest quality grades. No traces of treatment are revealed on thefinished surface when investigated under a l20-magnification microscope.Like in the above-stated example, superficial strengthening of the partstakes place.

EXAMPLE 3 Treatment of carbon-steel blanks of trunnions for measuringgears of electric measuring instruments is involved, the length of theeffective portion of a blank being equal to 1 mm. and its diameter equalto 0.5 mm.

In a container which holds l cc. of an inert fluid composed of 9.5 cc.of kerosene and 0.5 cc. of bone oil, are introduced 200 mg. of abrasivepowder, 20 grams of 1.2 mm. diameter globules or pellets made ofhigh-tin bronze, and 500 parts to be treated.

Then the container is imparted oscillating motion at a frequency of 50c./s. and an amplitude of 4 mm. Once the 40 hr. working cycle has beencompleted, the inert fluid is drained off and a mixture of parts andglobules is rinsed in gasoline and dried.

The finished trunnions are separated out from the globules by sievingthrough a screen having its meshes shaped to suit the shape of thefinished trunnions, while the globules are ready to be employed fortreating fresh lots of parts. The finished trunnions feature the qualityof surface finish on the effective portion thereof as to comply with thehighest quality grades. No traces of treatment are found on the finishedsurface when investigated under a IZO -magnification microscope. Similarto the examples 1 and 2 above, a superficial strengthening of the partsoccurs.

What we claim is:

l. A method of vibroabrasion treatment of small-sized parts in an inertliquid medium, comprising introducing into said inert liquid mediumabrasive powder and metallic bodies in a I predetermined ratio, saidmetallic bodies being constituted so as to be capable of fixing theabrasive powder particles on their surface and grinding them whileinteracting with said abrasive powder in the course of treatment of thesmall-sized parts involved, and vibrating said inert liquid mediumtogether with the small-sized parts under treatment, and abrasive powderand metallic bodies immersed therein.

2. A method of vibroabrasion treatment of small-sized parts in an inertliquid medium as claimed in claim 1, in which the abrasive powderintroduced into the inert liquid medium, is constituted such that itsgranularity effects the initial course grinding stage of treatment ofthe small-sized parts involved, the quantitative ratio between themetallic bodies and abrasive powder that are introduced into said inertliquid medium being such so as to provide a successive and completegrinding of the abrasive powder until obtaining the granularitynecessary to perform the final buffing stage of treating saidsmall-sized parts.

3. A method of vibroabrasion treatment of small-sized parts in an inertliquid medium as claimed in claim 1, in which introduced into said inertliquid medium are the metallic bodies which are constituted of high-tinbronze.

4. A method of vibroabrasion treatment of small-sized parts in an inertliquid medium as claimed in claim 2, in which introduced into said inertliquid medium are the metallic bodies which are constituted of high-tinbronze.

5. A method of vibroabrasion treatment of smallsized parts in an inertliquid medium as claimed in claim 1, in which the abrasive powder andmetallic bodies are introduced into the medium constituted of at leasttwo fluids different in viscosity.

2. A method of vibroabrasion treatment of small-sized parts in an inertliquid medium as claimed in claim 1, in which the abrasive powderintroduced into the inert liquid medium, is constituted such that itsgranularity effects the initial course grinding staGe of treatment ofthe small-sized parts involved, the quantitative ratio between themetallic bodies and abrasive powder that are introduced into said inertliquid medium being such so as to provide a successive and completegrinding of the abrasive powder until obtaining the granularitynecessary to perform the final buffing stage of treating saidsmall-sized parts.
 3. A method of vibroabrasion treatment of small-sizedparts in an inert liquid medium as claimed in claim 1, in whichintroduced into said inert liquid medium are the metallic bodies whichare constituted of high-tin bronze.
 4. A method of vibroabrasiontreatment of small-sized parts in an inert liquid medium as claimed inclaim 2, in which introduced into said inert liquid medium are themetallic bodies which are constituted of high-tin bronze.
 5. A method ofvibroabrasion treatment of small-sized parts in an inert liquid mediumas claimed in claim 1, in which the abrasive powder and metallic bodiesare introduced into the medium constituted of at least two fluidsdifferent in viscosity.